1. Field of the Invention
This invention relates to an electronic equipment having the function of displaying the battery residual quantity for displaying the usable residual time of a battery pack used as a power source of the electronic equipments, such as a video camera, portable telephone or a personal computer. The invention also relates to a method for displaying the battery residual quantity.
2. Description of the Related Art
Up to now, a battery pack constituted by a secondary cell, such as a lithium ion cell, NiCd cell or a nickel hydrogen cell, is well-known.
In many of this known type of the battery pack, there are enclosed a micro-computer for calculating the battery residual quantity for having communication with an electronic equipment having the battery as the power source, a peripheral circuit for the micro-computer and a battery cell status detection circuit required for the micro-computer to execute the calculations of the battery residual quantity.
On a variety of electronic equipments loaded with the above-mentioned battery packs, a display device is sometimes mounted for displaying the residual battery capacity. In many of the conventional electronic equipments, having this sort of the display device, the residual battery capacity is calculated and displayed on the basis of the terminal voltage of the battery power source (terminal voltage of the battery pack).
However, with the method for calculating the residual battery capacity from the terminal voltage of the battery power source, the following problems arise.
First, if discharging properties, that is the battery terminal voltage to discharging voltage characteristics, differ with the types of the battery cell, it is necessary to have an equation for conversion from the terminal voltage to the residual battery capacity from one battery cell to another, such that it is difficult to cope with future versions of the battery cell.
Second, the residual battery capacity after all specifies the ratio in percentage of the residual capacity to capacity of the fully charged battery, while the remaining usable time of the battery cannot be known from it.
Third, in the current state of the art, the residual battery capacity can be grasped from the discharge characteristics only roughly by gross levels, such as in four stages.
It is therefore an object of the present invention to provide an electronic equipment having the function of displaying the battery residual quantity, and a method for displaying the battery residual quantity, whereby it is possible to accommodate different types of the battery cell or future versions of the battery cell, while it is also possible to know the usable residual service life of the battery with high display accuracy.
With the electronic equipment having the function of displaying the residual battery capacity and the method for displaying the residual battery capacity according to the present invention, the information on the residual battery capacity, charging/discharging current detection information and the battery cell voltage detection information from the battery pack are received, the current residual battery capacity is calculated based on the received information, and the residual battery capacity is displayed based on the results of calculations.
That is, according to the present invention, the information on the residual battery capacity, charging/discharging current detection information and the battery cell voltage detection information are sent from the battery pack to the electronic equipment, which then calculates the residual battery capacity from the received information for display. Thus it becomes possible to accommodate different types of the battery cell or future versions of the battery cell, while it is also possible to know the usable residual service life of the battery with high display accuracy.